The present invention relates to sheet handling mechanisms, especially mechanisms for arranging sheets in overlapped relation, and/or arranging them into a horizontal stack.
Sheet stacking mechanisms have been heretofore proposed in which a series of sheets are overlapped and then arranged in a horizontal stack wherein the individual sheets are vertically oriented. Exemplary of mechanisms and techniques which overlap sheets and/or arrange sheets into a horizontal stack are those disclosed in U.S. Pat. Nos. 3,198,046 issued to DeAngelo on Aug. 3, 1965, 3,672,667 issued to Pahlitzsch on June 27, 1972, 3,932,982 issued to Klapp on Jan. 20, 1976, and 3,942,786 issued to Lauren on Mar. 9, 1976.
Mechanisms for overlapping sheets may involve a first conveyor which advances the sheets horizontally in sequence. The sheets are fed onto a more slowly traveling second conveyor so that the leading edge of a sheet on the first conveyor overtakes the trailing edge of the preceeding sheet on the second conveyor. Means is provided for physically raising such trailing edge relative to the leading edge of the succeeding sheet so that the latter may advance beneath the former. Thereafter, the trailing edge is permitted to descend upon the leading edge whereby the sheets are in lapped relation to facilitate subsequent stacking. The above-mentioned DeAngelo and Phlitzach patents are exemplary of such a mechanism.
In DeAngelo an air nozzle is utilized to produce blasts of air beneath the trailing edge to raise the latter. In Pahlitzsch that function is performed by cams which move relative to a suction conveyor carrying the preceding sheet.
It will be realized that the provision of sheet-raising devices, such as air nozzles or moving cams, renders the handling mechanism more complex and expensive and necessitates that precautions be taken to insure that the sheet-raising device is properly synchronized relative to the speed of the conveyors.
One manner of stacking overlapped sheets heretofore proposed involves the use of a pair of mutually opposite endless conveyors, one being of concave configuration, the other of convex configuration. These conveyors form a nip therebetween to grip and advance prelapped sheets from a horizontal orientation to a vertical orientation, whereupon the sheets are dropped into a conveyor-driven trough. As the sheets build-up in the trough, a horizontal stack is established. The aforementioned Klapp patent is exemplary of such a proposal.
The use of a pair of conveyor belts to transport sheets sandwiched therebetween and a driven trough into which the sheets are deposited, constitutes a complex and somewhat unweildy mechanism. If both belts are not driven at identical speeds, damage to the sheets may occur; hence precautions in that area must be taken. The driven trough makes further energy demands on the system, and its speed must be synchronized relative to the rate of sheet feed or else the sheets will not be stacked tightly.
It is, therefore, an object of the present invention to provide a novel sheet handling apparatus which solves or alleviates problems of the above-noted type.
It is another object of the present invention to provide novel apparatus for overlapping sheets.
It is another object of the present invention to provide novel apparatus for arranging sheets in a horizontal stack.
It is another object of the invention to overlap sheets and/or arrange sheets in a horizontal stack, by means of relatively simplified apparatus that are capable of relatively high-speed operation.
It is a further object of the invention to provide such apparatus which involve minimal concern for speed synchronization of sheet transport components.
It is another object of the invention to overlap sheets by advancing sheets onto a downwardly curved suction conveyor such that the act of adhering to the conveyor causes the trailing edge to be raised sufficiently to receive therebeneath the leading edge of the succeeding sheet.
It is still a further object of the invention to arrange overlapped sheets into a horizontal stack by advancing the sheets on a downwardly curved suction conveyor and dropping the sheets onto a displaceable carrier, the carrier being moved by the build-up of sheets thereon.